1. Field of the Invention
This invention relates to a flexible hose made primarily of polymeric material and to a method of making the same.
2. Prior Art Statement
It is known in the art to provide a hose made primarily of polymeric material and comprised of an inner base tube, a tubular braided reinforcing layer or reinforcing braid made of aramid yarn disposed concentrically around the base tube, and a polymeric cover tube disposed by extrusion process concentrically around the reinforcing braid. Because the aramid yarn of the reinforcing braid has a great affinity for water, previously proposed polymeric hose have water moisture created bubbles at the interface of the cover tube and reinforcing braid resulting in corresponding void spaces between the reinforcing braid and cover tube and thus a hose of comparatively poor quality.
Various techniques have been proposed to solve this problem such as drying of the braided aramid yarn in a suitable oven or heat tunnel immediately before extruding the cover tube thereover; however, these techniques have not been entirely successful and even with some practical use of prior drying of the braided aramid yarn there is a tendency for water moisture to collect on the braid causing bubbles on the tubular zone between the reinforcing braid and cover tube. If the drying times and/or temperatures are substantially increased there is often permanent damaging distortion of the inner base tube.
It has also been proposed to provide a plastisol adhesive against the braided aramid yarn followed by suitably curing such adhesive as with fire rings and with the plastisol adhesive still in a hot condition a polymeric cover tube is extruded against the reinforcing braid. However, even with this approach, the great affinity of the aramid reinforcing braid for water causes beading of water droplets in the tubular zone between such braid and cover tube and the formation of bubbles in such zone.